Brake Proportioning Valves - I need the low down...

Tell me about the 2 kinds of brake proportioning valves, the set style that seems to be a Chevy thing and the adjustable after market type.

When and how to do choose the item you need and is there any instance where both maybe employed on a project.

I have a 1960 F100 with bigger than stock rear drum brakes
(1962 Galaxie) and I know prior to taking it off the road for its rebuild that the rear was way over braked.
Since then I have installed a Dakota disc braked IFS and purchased a after market brake booster kit which incorporates the Chevy style set proportioning unit you see in the pic's below.

Will that set proportioning unit be able to manage my over braked rear end.

Any suggestions, advice and words of experience would be appreciated.

 

set prop valves are not going to be perfect due to all the variables in a build. If you have an adjustable, you're ahead of the game.

First off- you can never be over braked in the rear you just need more tire to use it,lol --- ok, that's a joke, and NOT true.


set it and get somewhere safe to test it in panic stops (dont forget to consider p***engers/cargo/weight)

remember that during a panic stop the front tires must lock up first (ideally-RIGHT before the rears) - that allows the rears to brake, when the fronts are sliding, keeping the car straight.

if the rears lock up first while the fronts are still slowing the car, then the back end WILL step out and you may just end up looping it, or worse.

I see it as an excuse for bigger rear tires, haha...

-rick

 

Throw the "Chevy thing" in the trash can and if you got extra money to throw behind it then buy the other one, but neither are necessary.....

 

X2 on what 69fury said. I have bigs & littles on the '57 and was told by the manufacturer that the adjustable unit was the only way to go. Use it in line with the rear brakes (dual MC,right?) and adjust it down till the fronts lock up 1st. Ya never want the back end to p*** the front!

 

First one you show is a "combination valve" , combines metering and proportioning.The metering portion doesn't allow the fronts to work until the backs see a certain amount of pressure. Since there's more take up on drums than discs, this gives the drums a chance to catch up. While you don't want the rears to lock up more, you also don't want the fronts to lock up too soon. This is nice when giving it a little brake when it's slippery. If the fronts lock too easily or too soon, you're not stopping as quickly as you'd like to and you also lose the ability to steer.

I'd try that one first, if you need more proportioning you can add an adjustable one in line one too.

 

I found that although I installed an adjustable valve when I built my brake system the rear brakes seem to work the best with it all the way open (full rear pressure). Probably cause of the big wheels and tires. Lot's to stop.

 

I'm in the process of plumbing the brake lines for our wagon and I agree with most, put an adjustable prop. valve for the the rear and dial it in in an empty parking lot with some panic stops. I won't be using the production-style metering/proportioning valve. However, my thoughts on when the brakes lock up are slightly different. I would prefer that the rear lock up JUST BEFORE the fronts so steering with front wheels turning is still an option before loosing vehicle control(like I would admit loss of control anyway). Everybody has differing driving styles; that's the beauty of an adj. prop. valve, get it set where you feel it gives you the most confident braking control and you're good to go.
JM$.02

 

Let's see...suggestions, advice and words of experience.

Yes, most of what has been posted on this thread so far is garbage and will get your a** killed in an all-out panic stop.

69fury has it pretty well summed up, however it would be a great idea to do a subject search to get more information. This is no place to rely on half-fast opinions.

Here's what you will find, in a nutshell:

1. Be sure your fluid lines are hooked up correctly.

2. Install a 2 lb. residual pressure valve to the front brakes...even if you don't think you need one.

3. Be sure to install a 10 lb. residual pressure valve to the rear brakes...even if you don't think you need one.

4. Be sure your rear brakes are adjusted correctly.

5. Be sure you have bled all the air out of the system.

6. Be sure your tires are inflated to the proper pressures; average two people and a half tank of gas.

7. Find a safe area and do some test stops from gradually increasing speeds with an outside (non-riding) observer to tell you which tires lock up first.

Ideally the fronts will lock up just before the rears.

8. If the rears lock up first, install an adjustable pressure regulator and reduce the pressure to the rear brakes until the fronts lock up first.

Drive safely.

 

So whats the deal on drum/drum setups? I've been told that because my car is now lowered, causing the master cylinder to be lower than the slave cylinders, i will get fluid running back to the master cylinder, and so momentarily no brakes. I have been advised to install residual valves just after the master cylinder to stop this happening. is this right? Its stock drums in a 40 with a late model manual dual circuit master cylinder under the floor, car lowered all round. Hope you dont mind the thread hijack fiftyv8.....

 

No Buddy, the more the more discussion on this topic the better, we can always pick up something new.

 

If you are running a master cylinder for drum brakes, it likely will have the residual pressure valves in the ports already. Did it brake and have good pedal feel before lowering? If so, you will not need to install additional ones. If you were pumping the pedal one or two times to get a "good" pedal, then you likely needed them and still do.